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Thursday, September 12, 2013

Pleasant weekend ahead with fall-like weather!

Synopsis

Another hot and muggy day across the Mid-South with thunderstorms dotting the area. Currently a cold front situated to our north will make its way south through the area tonight, bringing with it a major change in our weather. Above average temperatures for this time of year will quickly change to below average temperatures as fall-like weather overtakes the region.

Analysis

Surface Analysis as of 10am Thursday

A look at the national picture shows the aforementioned cold front extending from the northeastern US to the Arkansas/Missouri border.

Visible Satellite at 2pm CDT Thursday

This feature is also quite apparent on visible satellite imagery with scattered thunderstorms across areas south of the cold front.

Sept 12, 12Z (7am CDT) GFS modeled 500 mb Relative Vorticity

This upper-level (18,000') map shows the longwave trough of low-pressure responsible for the cold front moving through the area Friday morning. There is not much energy that would support lifting available during the cold front passage. This in combination with little convection due to it being the morning hours suggests little to no precipitation associated with the passage of the cold front.

Sept 12 12Z (7am) GFS modeled 850 mb (5,000') Temperatures

Looking at lower levels of the atmosphere (5,000') mid-day Friday, we see significant cold air advection. Basically this map is showing us much colder air to our north being blown into the Mid-South, resulting in much cooler, drier conditions. This particular model is even overdoing the temperatures by quite a bit, predicting temperatures to drop to 50 degrees or even lower tomorrow night. This is because the models do not really distinguish the seasons very well without inputting climatological records. Once these records are put into the model we get much more appropriate temperatures in return which we then interpret accordingly.

Wiliam's Memphis Forecast

Friday: Some morning clouds clearing by noon with a high of 81, low of 57.